A Better Bug for Biofuels

While most attempts to engineer biofuel-producing microbes have focused on well-known organisms such as yeasts and E. coli, scientists also hope to co-opt the unique metabolic functions of some of the microbial world's less-studied creatures. Anthony Sinskey and his team at MIT have been cataloguing the genomic secrets of Rhodococcus bacteria, soil-dwelling microbes known to eat a variety of toxic compounds. The goal is to make a biodiesel-producing organism that can use a variety of sources as fuel. "We have done a lot of the basic chemistry and biology," says Sinskey. "Now we need to figure out how to maximize yields."

The strain of bacteria that Sinskey is working on, Rhodococcus opacus, is related to the type that causes tuberculosis, but it has two particularly appealing qualities. The bacteria have a flexible appetite, with the ability to eat a number of sugars and toxic compounds--in fact, the microbes were originally isolated from contaminated soil, where they were breaking down petroleum waste products. In addition, R. opacus are one of just a few types of bacteria that naturally produce a type of lipid called tryacylglycerols, which can be chemically converted into biodiesel. "Its life is focused around lipid metabolism, eating weird lipids and making more of them," says Jason Holder, a postdoctoral researcher in Sinskey's lab. "The trick is to engineer them to make it more efficiently, using waste streams of carbon."